In ancient times, people were recording the time according to the natural phenomenon of the ascent and descent of the sun and of the moon. However, the change of the natural phenomenon of the ascent and descent of the sun and of the moon may vary with the change of season, location, and weather.
It is an outstanding achievement in human history to have quantitatively divided a day into 24 hours, an hour into 60 minutes, and a minute into 60 seconds, and to have divided the world into 24 time zones. As a consequence, the application of time conversion helps in deciding at which times to set up communication between two areas in the world, which are remote from one another.
Following the fast development in transportation and telecommunication, the land we live on has become a small world. An event which happens at one place may be instantly transmitted and noticed by people who live in another continent. In order to meet actual requirements in daily affairs, time conversion has become more and more important.
The conventional method to display the time for specific time zones, as commonly adopted by international standard hotels, is to display the time for respective time zones on several wall clocks simultaneously.
Recently there has become known a kind of table clock for a time conversion display, which includes a base having a plurality of time recording elements to display the time for a respective time zone. However, this kind of time conversion clock is not very satisfactory in application, and has various drawbacks, as outlined hereinunder:
(1) It is heavy and expensive. Because is requires several time recording elements, its size and manufacturing cost cannot easily be minimized.
(2) It provides only a limited time display. Because it can only display time for a limited number of time zones, it cannot be regarded as a "universal clock".
(3) It is difficult to regulate and maintain. Because it includes various time recording elements, its regulation and maintenance process becomes more complicated and cumbersome.